Former first lady Nancy Reagan will be laid to rest today in Simi Valley, Calif. She was a remarkable woman.

Overlooked in discussions of her role as the devoted wife is how she forever changed the role of first lady. It was a role that was markedly different from any before her but one that will be studied and often copied by her successors.

Eleanor Roosevelt showed that a first lady could be an activist. Both publicly and behind the scenes she lobbied her husband. Sometimes unsuccessfully.

A very dramatic example was her reaction to learning of the death camps in Germany toward the end of World War II. Information now available to researchers shows that the first lady lobbied her husband to bomb the camps. It was an idea suggested by a member of the president's cabinet.

The thinking was that the bombing was risky to the inmates but it would disrupt the process and possibly allow for a mass escape. In retrospect, it might have saved hundreds of thousands of lives.

But FDR and his wife Eleanor were estranged and there were limits to what she could accomplish. Toward the end of his life, FDR brought in his own daughter, Anna, as a super White House staffer.

Among other things she was tapped to run interference with Eleanor as FDR renewed his liaison with an old girlfriend. There is a scene in my book, "All the Presidents' Children," where Eleanor confronts her daughter Anna, begging to go to the summit in Yalta. On orders from FDR, Anna turns her down.

Lady Bird Johnson was a superb businesswoman, who later took the Johnson business interests to new heights but as first lady, she assumed the traditional role, never contradicting her husband.

Rosalynn Carter took activism to new lengths when she actually sat in on many of her husband's Cabinet meetings.

But in general, before Nancy Reagan, the role of first lady was indivisible from the role of husbands on policy and personnel.

Nancy Reagan broke from her husband on both even while they were seen as utterly devoted to each.

When it came to White House personnel she became known as the "great enforcer." Any one disloyal or incompetent or politically damaging would get pushed out. The president could maintain his relationship with the former staffer. It could all be blamed on "that mean old first lady."

Likewise, stories would leak that the first lady held a different view on a particular issue.

This allowed the president to expand his political base and engage with editors, television producers and politicians outside of his ideological circle. This was so effective that it was repeated by subsequent first ladies. Barbara Bush let it leak that she had different views on pro-choice. Laura Bush let it leak that she was not happy with the president's language, "wanted dead or alive."

If the president had let another staffer disagree on policy or personnel he would have appeared weak. But his support of his wife's role only made him appear loyal.

This arrangement worked especially well for the Reagans because they were so publicly devoted to each other. Frank and Claire Underwood would never have gotten away with it.

She was also the doorway in for anyone who could help her husband and who could serve him loyally. And she knew how to spot them.

Doug Wead is a presidential historian who served as a senior adviser to the Ron Paul presidential campaign. He is a New York Times best-selling author, philanthropist, and adviser to two presidents, including President George H.W. Bush, with whom he co-authored the book "Man of Integrity." Read more reports from Doug Wead — Click Here Now.